1. Field of the Invention:
The present invention relates to a thermally insulating sash frame member, and more particularly to improvements in weatherproofing for such sash frame member.
2. Prior Art:
A known thermally insulating sash frame member comprises a pair of spaced interior and exterior metallic bars interconnected by a thermally insulating connector bar. Each of the interior and exterior bars has a pair of gripping flanges projecting from one of their confronting inner walls. For assembly, the connector bar is placed between the interior and exterior bars, and then the two pairs of gripping flanges are forced or bent to grip the connector bar at opposite sides through the length thereof. However, the connector bar is usually made of rigid material such as rigid polyvinyl chloride, and for this reason, the gripping flanges can engage with the connector bar with only inadequate weathertightness. For the same reason, firm connection between the connector bar and the interior and exterior bars is difficult to achieve.